Addition-curable silicone resin composition and a semiconductor device

ABSTRACT

One of the purposes of the present invention is to provide an addition-curable silicone composition which provides a cured product having good performance at a low temperature and excellent resistance to a temperature change, and to provide a semiconductor device having a high reliability, whose semiconductor element is encapsulated with a product obtained by curing the addition-curable silicone composition. Thus, an addition-curable silicone resin composition comprising (A) a branched organopolysiloxane represented by the following formula (1): 
                         
wherein a is an integer of from 2 to 100, b is an integer of from 5 to 100, c is an integer of from 5 to 100, 0.03≤a/(a+b)&lt;1.0, and a ratio of the number of (R 1   2 R 2 SiO 1/2 ) unit to the number of (R 2 SiO 3/2 ) unit is 2 or less; (B) an organopolysiloxane represented by the following formula (2): (R 2   3 SiO 1/2 ) r (R 2   2 SiO 2/2 ) s (R 2 SiO 3/2 ) t (SiO 4/2 ) u  (2) in an amount of 5 to 900 parts by mass, relative to 100 parts by mass of component (A); (C) an organopolysiloxane having at least two hydrosilyl groups, in an amount such that a ratio of the number of the hydrosilyl groups in component (C) to the number of the alkenyl groups in components (A) and (B) is 0.4 to 4.0; and (D) a hydrosilylation catalyst in an amount sufficient to accelerate hydrosilylation.

CROSS REFERENCE

This application claims the benefits of Japanese Patent Application Nos.2015-249457 filed on Dec. 22, 2015, and 2016-128007 filed on Jun. 28,2016, the contents of which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an addition-curable siliconecomposition and a semiconductor device provided with a cured productthereof. Specifically, the present invention relates to anaddition-curable silicone composition comprising an alkenylgroup-containing branched organopolysiloxane with a long siloxanebranch.

Addition-curable silicone resins have good heat resistance and lightresistance and a high curing rate, so that they have been used asmaterials for encapsulating semiconductor elements such as LEDs. Forinstance, Japanese Patent Application Laid-Open No. 2006-256603describes an addition-curable silicone resin having high adhesiveness toan LED package made of a thermoplastic resin such as PPA. JapanesePatent Application Laid-Open No. 2006-93354 describes a method forencapsulating an optical semiconductor element with an addition-curablesilicone resin composition by compression molding.

As mentioned above, addition-curable silicone resins are generally usedas materials for encapsulating semiconductor elements, but theirperformances are not sufficient. Particularly, it is important formaterials encapsulating LEDs to have low-temperature resistance inaddition to heat resistance and light resistance because theencapsulating materials are exposed to external stress such as changesof temperature and humidity of the atmosphere in addition to internalstress such as temperature change caused by switching an opticalsemiconductor device on and off. However, the conventionaladdition-curable silicone resins show insufficient performance at a lowtemperature and do not endure stress caused by temperature change,resulting in poor crack resistances.

It is known that introduction of a branch structure into a linearsilicone chain is efficient as one of methods to improve alow-temperature property of a cured silicone resin. Japanese PatentApplication Laid-Open Nos. 2006-256603, 2006-93354 and 2002-348377describe methods for preparing such silicone resins. However, the methodfor preparing a branched organopolysiloxane by having a hydrolyzablesilane having an R³SiO_(1/2) unit [M unit] and an RSiO_(3/2) unit [Tunit] to cause a condensation or an equilibration reaction in thepresence of an acid catalyst or an alkali catalyst cannot separatelycontrol a length of the main chain and a length of the side chain.Accordingly, it was difficult to obtain a siloxane with a desiredstructure.

PRIOR LITERATURES Patent Literatures

-   [Patent Literature 1] Japanese Patent Application Laid-Open No.    2006-256603-   [Patent Literature 2] Japanese Patent Application Laid-Open No.    2006-93354-   [Patent Literature 3] Japanese Patent Application Laid-Open No.    2002-348377-   [Patent Literature 4] Japanese Patent Application Laid-Open No.    2001-163981-   [Patent Literature 5] Japanese Patent Application Laid-Open No.    2000-351949

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

One of the purposes of the present invention is to provide anaddition-curable silicone composition which provides a cured producthaving good performance at a low temperature and excellent resistance toa temperature change, and to provide a semiconductor device having ahigh reliability, which semiconductor element is encapsulated with thecured product of the addition-curable silicone composition.

Means to Solve the Problems

Thus, the present invention provides an addition-curable silicone resincomposition comprising

(A) a branched organopolysiloxane represented by the following formula(1):

wherein R¹ is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atomsor a substituted or unsubstituted, aromatic hydrocarbon group having 6to 12 carbon atoms, R² is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,a substituted or unsubstituted, aromatic hydrocarbon group having 6 to12 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, R¹ andR² may be the same as or different from each other, at least two of R²are each an alkenyl group, a is an integer of from 2 to 100, b is aninteger of from 5 to 100, c is an integer of from 5 to 100,0.03≤a/(a+b)<1.0, and a ratio of the number of (R¹ ₂R²SiO_(1/2)) unit tothe number of (R²SiO₃/2) unit is 2 or less, wherein the parenthesizedsiloxane units may bond randomly or form a block unit;

(B) an organopolysiloxane represented by the following formula (2):(R² ₃SiO_(1/2))_(r)(R² ₂SiO_(2/2))_(s)(R²SiO_(3/2))_(t)(SiO_(4/2))_(u)  (2)wherein R² is as defined above, at least two of R² are each an alkenylgroup, r is an integer of from 0 to 100, s is an integer of from 0 to300, t is an integer of from 0 to 200, and u is an integer of from 0 to200, provided that a total of t and u is 1 to 400 and a total of r, s, tand u is 2 to 800,

in an amount of 5 to 900 parts by mass, relative to 100 parts by mass ofcomponent (A),

(C) an organopolysiloxane having at least two hydrosilyl groups, in anamount such that a ratio of the number of the hydrosilyl groups incomponent (C) to the number of the alkenyl groups in components (A) and(3) is 0.4 to 4.0, and

(D) a hydrosilylation catalyst in an amount sufficient to acceleratehydrosilylation.

Effects of the Invention

According to the present invention, the composition comprising analkenyl group-containing branched organopolysiloxane which has a lot ofthe siloxane units having sufficiently longer branch, compared to a mainsiloxane chain, in combination of the other specific components,provides a cured product which has a lower glass-transition temperatureand improved crack resistance, compared to a composition comprising alinear organopolysiloxane which has a similar length of a siloxanechain.

BRIEF EXPLANATION OF THE DRAWING

FIG. 1 shows a graph of the storage elastic modulus and the tangent δsin Example 1 (solid line) and Comparative Example 1 (dotted line).

BEST MODE OF THE INVENTION

The present invention will be described below in detail.

(A) Branched Organopolysiloxane

The branched polyorganosiloxane (A) is one of the characteristics of thepresent invention and is represented by the following formula:

wherein R¹ is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atomsor a substituted or unsubstituted, aromatic hydrocarbon group having 6to 12 carbon atoms, R² is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,a substituted or unsubstituted, aromatic hydrocarbon group having 6 to12 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, R¹ andR² may be the same as or different from each other, at least two of R²are each an alkenyl group, a is an integer of from 2 to 100, b is aninteger of from 5 to 100, c is an integer of from 5 to 100,0.03≤a/(a+b)<1.0, and a ratio of the number of (R¹ ₂R²SiO_(1/2)) unit tothe number of (R²SiO_(3/2)) unit is 2 or less, wherein the parenthesizedsiloxane units may bond randomly or form a block unit.

a is an integer of from 2 to 100, preferably an integer of from 2 to 75,further preferably an integer of from 2 to 50. b is an integer of from 5to 100, preferably an integer of from 5 to 75, further preferably 10 to50. c is an integer of from 5 to 100, preferably an integer of from 5 to75, further preferably 10 to 50. A ratio of the number of (R¹₂R²SiO_(1/2)) unit to the number of (R²SiO_(3/2)) unit is 2 or less. Theparenthesized siloxane units may bond randomly or form a block unit. Inthe formula (1), 0.03≤a/(a+b)<1.0, further preferably 0.09≤a/(a+b)≤0.9.

R¹ is, independently of each other, a substituted or unsubstituted,saturated hydrocarbon group having 1 to 12 carbon atoms, or asubstituted or unsubstituted, aromatic hydrocarbon group having 6 to 12carbon atoms. Examples of the saturated hydrocarbon group include alkylgroups such as a methyl group, an ethyl group, a propyl group, a butylgroup, and an octyl group, and cycloalkyl groups such as a cyclopentylgroup and a cyclohexyl group; and those hydrocarbon groups wherein apart or all of the hydrogen atoms are substituted with a substituentsuch as a halogen atom such as a fluorine atom, a bromine atom and achlorine atom or a cyano group, e.g., halogen-substituted monovalenthydrocarbon groups such as trifluoropropyl and chloropropyl groups,cyanoalkyl groups such as a β-cyanoethyl group and a γ-cyanopropylgroup, a 3-methacryloxypropyl group, a 3-glycidyloxypropyl group, a3-mercaptopropyl group, and a 3-aminopropyl group. Among these, a methylgroup and a cyclohexyl group are preferred. A methyl group is morepreferred. Examples of the aromatic hydrocarbon group include arylgroups such as a phenyl group, a tolyl group and a naphthyl group, andaralkyl groups such as a benzyl group, a phenylethyl group and aphenylpropyl group; and those wherein a part or all of the hydrogenatoms bonded to the carbon atoms are substituted with a substituent suchas a halogen atom such as a fluorine atom, a bromine atom and a chlorineatom, or a cyano group. Among these, a phenyl group and a tolyl groupare preferred. A phenyl group is more preferred. At least one of R¹ isan aromatic hydrocarbon group having 6 to 12 carbon atoms.

R² is, independently of each other, selected from a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,preferably 1 to 8 carbon atoms, a substituted or unsubstituted, aromatichydrocarbon group having 6 to 12 carbon atoms, preferably 6 to 10 carbonatoms, and an alkenyl group having 2 to 10 carbon atoms, preferably 2 to8 carbon atoms. Examples of the saturated hydrocarbon group and thearomatic hydrocarbon group may be those groups defined for R. Examplesof the alkenyl group include a vinyl group, an allyl group, a propenylgroup, a hexenyl group and a styryl group. Among these, a vinyl groupand an allyl group are preferred, and a vinyl group is furtherpreferred.

In component (A), the number of the monovalent aromatic hydrocarbongroup bonded to a silicon atom is preferably 3% or more, furtherpreferably 5% or more, and 90% or less, further preferably 80% or less,based on a total number of the groups each bonded to a silicon atom.When the branched organopolysiloxane (A) has the monovalent aromatichydrocarbon group in the aforesaid amount, a cured product from (A) hasa higher refraction index and a lower gas permeability, so that thecomposition is suitable for encapsulating semiconductor elements.

The branched organopolysiloxane may be prepared in a method comprisingsteps of

subjecting an organopolysiloxane represented by the following formula(4):

wherein R¹, R² and c are as defined above, and R³ is a hydrogen atom ora saturated hydrocarbon group having 1 to 6 carbon atoms,to a co-condensation reaction with other siloxanes such as anorganopolysiloxane which has alkoxysilyl groups or hydroxysilyl groups,i.e. silanol groups, at both terminals and is represented by thefollowing formula (5):

wherein R² and R³ are as defined above, b′ is at least 1 and at mostsame as b, and b is as defined above,subsequently an end-capping reaction with other silane such as ahydrolyzable group-containing silane compound represented by thefollowing formula (6):

wherein R¹ and R² are as defined above, X is a halogen atom or a grouprepresented by R³O—, wherein R³ is as defined above, to thereby obtain abranched organopolysiloxane (A).In the formula (4), R³ is a hydrogen atom or a saturated hydrocarbongroup having 1 to 6 carbon atoms, such as a methyl group, an ethylgroup, a propyl group, a butyl group, an isopropyl group, a hexyl groupand a cyclohexyl group. Among these, a methyl group and an ethyl groupare preferred. A methyl group is particularly preferred.

The organopolysiloxane having two alkoxy groups at one terminal may besynthesized in any known manners. For instance, Japanese PatentApplication Laid-Open No. Sho 59-78236 describes a method where a cyclicsilicon compound is ring-opening polymerized in the presence of a metalsilanolate as an initiator, the reaction at the terminal is stopped byan acid and, then, the terminal is reacted with a trialkoxysilane.Japanese Patent Application Laid-Open No. Hei 7-224168 describes that acyclic silicon compound is polymerized in the presence of a silanolcompound as an initiator and a pentacoordinate silicon as a catalystand, then, the terminal of the polymer obtained is reacted with atrialkoxysilane.

(B) Organosiloxane

(B) Organosiloxane is represented by the following formula (2):(R² ₃SiO_(1/2))_(r)(R² ₂SiO_(2/2))_(s)(R²SiO_(3/2))_(t)(SiO_(4/2))_(u)  (2)wherein R² is as defined above, at least two of R² are each an alkenylgroup, r is an integer of from 0 to 100, s is an integer of from 0 to300, t is an integer of from 0 to 200, and u is an integer of from 0 to200, provided that a total of t and u is 1 to 400 and a total of r, s, tand u is 2 to 800.

r is an integer of from 0 to 100, preferably an integer of from 0 to 75,further preferably an integer of from 0 to 50. s is an integer of from 0to 300, preferably an integer of from 0 to 200, further preferably aninteger of from 0 to 100. t is an integer of from 0 to 200, preferablyan integer of from 0 to 100, further preferably an integer of from 0 to50. u is an integer of from 0 to 200, preferably an integer of from 0 to100, further preferably an integer of from 0 to 50. A total of t and uis 1 to 400, preferably 1 to 200, further preferably 1 to 100. A totalof r, s, t and u is 2 to 800, preferably 2 to 400, further preferably 2to 200.

The examples of R² are as defined for component (A).

In component (B), the number of the monovalent aromatic hydrocarbongroup bonded to a silicon atom is preferably 3% or more, furtherpreferably 5% or more, and 90% or less, further preferably 80% or less,based on a total number of the groups each bonded to a silicon atom.When the branched organopolysiloxane (B) has the monovalent aromatichydrocarbon group in the aforesaid amount, the branchedorganopolysiloxane has a higher refraction index and a lower gaspermeability and is well compatible with component (A), so that thecured product has an excellent transparency and mechanical strength.Therefore, the composition is suitable for encapsulating semiconductorelements.

An amount of component (B) is 5 to 900 parts by mass, preferably 10 to800 parts by mass, further preferably 20 to 600 parts by mass, relativeto 100 parts by mass of component (A). When the composition comprisescomponent (B) in the aforesaid amount, a cured product is rubbery.

(C) Organopolysiloxane Having at Least Two Hydrosilyl Groups

The organopolysiloxane having at least two hydrosilyl groups ispreferably represented by the following formula (3), but is not limited.(R³ ₃SiO_(1/2))_(r′)(R³₂SiO_(2/2))_(s′)(R³SiO_(3/2))_(t′)(SiO_(4/2))_(u′)  (3)wherein R³ is, independently of each other, a hydrogen atom, asubstituted or unsubstituted, saturated hydrocarbon group having 1 to 12carbon atoms, or a substituted or unsubstituted, aromatic hydrocarbongroup having 6 to 12 carbon atoms, at least two of R³ are each ahydrogen atom, r′ is an integer of from 0 to 100, s′ is an integer offrom 0 to 300, t′ is an integer of from 0 to 200, u′ is an integer offrom 0 to 200, and a total of r′, s′, t′ and u′ is 2 to 800.

Examples of the substituted or unsubstituted, saturated hydrocarbongroup having 1 to 12 carbon atoms, and the substituted or unsubstituted,aromatic hydrocarbon group having 6 to 12 carbon atoms may be thosedefined for R¹. At least two of R³ are each a hydrogen atom and theremaining R³ is preferably a methyl group or a phenyl group. r′ is aninteger of from 0 to 100, preferably an integer of from 0 to 75, furtherpreferably an integer of from 0 to 50. s′ is an integer of from 0 to300, preferably an integer of from 0 to 200, further preferably aninteger of from 0 to 100. t′ is an integer of from 0 to 200, preferablyan integer of from 0 to 100, further preferably an integer of from 0 to50. u′ is an integer of from 0 to 200, preferably an integer of from 0to 100, further preferably an integer of from 0 to 50. A total of r′,s′, t′ and u′ is 2 to 800, preferably 2 to 400, further preferably 2 to200.

Component (C) has a monovalent aromatic hydrocarbon group bonded to asilicon atom, preferably in an amount of 3% or more, further preferably5% or more, to 80% or less in number, based on a total number of thegroups each bonded to a silicon atom. When the organopolysiloxane (C)has the aromatic hydrocarbon group in the aforesaid amount, the curedproduct has a higher refraction index; and a lower gas permeability andcomponent (C) is well compatible with components (A) and (B), so thatthe cured product has an excellent transparency. Therefore, thecomposition is suitable for encapsulating semiconductor elements.

An amount of component (C) may be such that a ratio of the number of thehydrosilyl groups in component (C) to a total number of the alkenylgroups in components (A) and (B) is 0.4 to 4, preferably 0.6 to 2.0,further preferably 0.8 to 1.6. If the amount is less than theafore-mentioned lower limit, the amount of an SiH group is insufficientand, thereby, curing does not proceed satisfactorily. If the amountexceeds the afore-mentioned upper limit, an unreacted SiH group cause aside reaction such as a dehydrogenation.

(D) Hydrosilylation Catalyst

Any known catalyst which can accelerate the hydrosilylation may be usedand not particularly limited. Preferred is a catalyst selected from anelement of the platinum group metals and a compound including an elementof the platinum group metals. Examples of these catalysts includeplatinum catalysts such as platinum, including platinum black, platinumchloride, a chloroplatinic acid, a complex of platinum with an olefinsuch as a complex of platinum with a divinylsiloxane, and a complex of aplatinum with a carbonyl; palladium catalysts; and rhodium catalysts.The catalyst may be used singly or two or more in combination of them.Preferred are chloroplatinic acid and a complex of platinum with anolefin such as a complex of platinum with divinylsiloxane.

Component (D) may be used in a catalytic amount. The catalytic amount issuch that the hydrosilylation is accelerated and may be properlydecided, depending on a desired curing rate. For instance, when aplatinum group metal catalyst is used, the amount, reduced to a platinumgroup metal, is preferably 1.0×10⁻⁴ to 1.0 part by mass, more preferably1.0×10⁻³ to 1.0×10⁻¹ part by mass, relative to the total 100 parts bymass of components (A), (B) and (C), in view of reactivity.

Optional Components

The present silicone composition may further comprise other additivessuch as a fluorescent material, an inorganic filler, anadhesion-imparting agent, and a curing inhibitor in addition tocomponents (A) to (D), if needed. Each of components will be explainedbelow in detail.

Fluorescent Material

Any conventional fluorescent material may be used and not particularlylimited. For instance, preferred is such that absorbs light generated bya semiconductor light-emitting diode having, as a light emitting layer,a semiconductor element, in particular a nitride semiconductor element,and converts its wavelength to different one. The fluorescent materialis preferably selected from, for instance, the group consisting ofnitride fluorescent materials and oxynitride fluorescent materials whichare activated mainly by lanthanide elements such as Eu and Ce;fluorescent materials activated mainly by lanthanide elements such as Euor by transition metal elements such as Mn, such as alkaline earth metalhalogen apatites, alkaline earth metal halogen borates, alkaline earthmetal aluminates, alkaline earth metal silicates, alkaline earth metalsulfides, alkaline earth metal thiogallates, alkaline earth metalsilicon nitrides and germinates; rare earth metal aluminates and rareearth metal silicates which are activated mainly by lanthanide elementssuch as Ce; organic fluorescent materials and organic complexfluorescent materials which are activated mainly by lanthanide elementssuch as Eu; and Ca—Al—Si—O—N type oxynitride glass fluorescentmaterials.

Examples of the nitride fluorescent material which is activated mainlyby lanthanide elements such as Eu and Ce include M₂Si₅N₈:Eu, MSi₇N₁₀:Eu,M_(1.8)Si₅O_(0.2)N₈:Eu and M_(0.9)Si₇O_(0.1)N₁₀:Eu, wherein M is atleast one selected from the group consisting of Sr, Ca, Ba, Mg and Zn.

Examples of the oxynitride fluorescent material which is activatedmainly by lanthanide elements such as Eu and Ce include MSi₂O₂N₂:Eu,wherein M is at least one selected from the group consisting of Sr, Ca,Ba, Mg and Zn.

Examples of the alkaline earth metal halogen apatite fluorescentmaterial which is activated mainly by lanthanide elements such as Eu ortransition metal elements such as Mn include M₅(PO₄)₃X:R, wherein M isat least one selected from the group consisting of Sr, Ca, Ba, Mg andZn, X is at least one selected from the group consisting of F, Cl, Brand I, and R is at least one of Eu and Mn.

Examples of the alkaline earth metal halogen borate fluorescent materialinclude M₂B₅O₉X:R, wherein M is at least one selected from the groupconsisting of Sr, Ca, Ba, Mg and Zn, X is at least one selected from thegroup consisting of F, Cl, Br and I, and R is at least one of Eu and Mn.

Examples of the alkaline earth metal aluminate fluorescent materialinclude SrAl₂O₄: R, Sr₄Al₁₄O₂₅:R, CaAl₂O₄: R, BaMg₂Al₁₆O₂₇:R,BaMg₂Al₁₆O₁₂:R and BaMgAl₁₀O₁₇:R, wherein R is at least one of Eu andMn.

Examples of the alkaline earth metal sulfide fluorescent materialinclude La₂O₂S:Eu, Y₂O₂S:Eu and Gd₂O₂S:Eu.

Examples of the rare earth metal aluminate fluorescent material which isactivated mainly by lanthanide elements such as Ce include YAG typefluorescent materials represented by compositional formulas:Y₃Al₅O₁₂:Ce, (Y_(0.8)Gd_(3.2))₃Al₅O₁₂:Ce, Y₃(Al_(0.8)Ga_(0.2))₅O₁₂:Ce,and (Y,Gd)₃(Al,Ga)₅O₁₂ and those compounds where a part or the whole ofY are replaced with Tb or Lu, such as Tb₃Al₅O₁₂:Ce and Lu₃Al₅O₁₂:Ce.

Examples of the other fluorescent materials include ZnS:Eu, Zn₂GeO₄:Mnand MGa₂S₄:Eu, wherein M is at least one selected from the groupconsisting of Sr, Ca, Ba, Mg and Zn, and X is at least one selected fromthe group consisting of F, 01, Br and I.

The afore-mentioned fluorescent materials may comprise at least oneselected from the group consisting of Tb, Cu, Ag, Au, Cr, Nd, Dy, Co, Niand Ti, in place of Eu or in addition to Eu, if needed.

The Ca—Al—Si—O—N type oxynitride glass fluorescent material comprises,as a matrix, oxynitride glass comprising 20 to 50 mole % of CaCO₃,calculated as CaO, 0 to 30 mole % of Al₂O₃, 25 to 60 mole % of SiO, 5 to50 mole % of AlN and 0.1 to 20 mole % of rare earth metal oxides ortransition metal oxides, wherein the total amount of the aforesaidcomponents is 100 mole %. The fluorescent material with the oxynitrideglass matrix preferably comprises nitrogen atoms in an amount of 15weight % or less and preferably comprises, besides rare earth metaloxides ions, the other rare earth metal ions which work as a sensitizerin an amount of 0.1 to 10 mole %, calculated as rare earth metal oxides,in the fluorescent glass as a co-activator.

Other fluorescent materials which have a similar function and providesimilar effects may be used.

An amount of the fluorescent material is preferably 0.1 to 2,000 partsby mass, more preferably 0.1 to 100 parts by mass, relative to 100 partsby mass of the components other than the fluorescent material, forinstance, 100 parts by mass of components (A) to (D). When the presentcured product is used as a wavelength conversion film comprising afluorescent material, the amount of the fluorescent material ispreferably 10 to 2,000 parts by mass. The fluorescent materialpreferably has a mean diameter of 10 nm or more, more preferably 10 nmto 10 μm, further preferably 10 nm to 1 μm. The mean diameter isdetermined from a particle size distribution obtained in a laserdiffraction method using a Cilas laser measurement instrument.

Inorganic Filler

Examples of the inorganic filler include silica, fumed silica, fumedtitanium dioxide, alumina, calcium carbonate, calcium silicate, titaniumdioxide, iron (III) oxide and zinc oxide. The inorganic filler may beused singly or in combination of two or more of them. An amount of theinorganic filler may be 20 parts by mass or less, preferably 0.1 to 10parts by mass, relative to total 100 parts by mass of components (A) to(D), but not limited to these.

Adhesion-Imparting Agent

The present silicone composition may comprise an adhesion-impartingagent in order to add adhesiveness to a cured product, if needed.Examples of the adhesion-imparting agent include organosiloxaneoligomers having at least two, preferably three, functional groupsselected from the group consisting of a hydrogen atom bonded to asilicon atom, an alkenyl group, an alkoxy group and an epoxy group. Theorganosiloxane oligomer preferably has 4 to 50 silicon atoms, morepreferably 4 to 20 silicon atoms. The adhesion-imparting agent may beorganooxysilyl-modified isocyanurate represented by the followinggeneral formula (7) or a hydrolysis and condensation product of thecompound, i.e. organosiloxane-modified isocyanurate.

R⁴ is, independently of each other, an organic group represented by thefollowing formula (8) or an unsaturated aliphatic monovalent hydrocarbongroup.

wherein R⁵ is a hydrogen atom or a monovalent hydrocarbon group having 1to 6 carbon atoms and k is an integer of from 1 to 6, preferably 1 to 4.

An amount of the adhesion-imparting agent is 10 parts by mass or less,preferably 0.1 to 8 parts by mass, more preferably 0.2 to 5 parts bymass, relative to total 100 parts by mass of components (A) to (D). Whenthe amount of the adhesion-imparting agent does not exceed the aforesaidupper limit, high hardness of the cured product is attained and surfacetackiness of the cured product is avoided.

Curing Inhibitor

The present silicone composition may further comprise a curing inhibitorin order to suppress the reactivity to improve storage stability.Examples of the curing inhibitor include triallylisocyanurate, alkylmaleate, acetylene alcohols, silane-modified or siloxane-modifiedproduct of these, hydroperoxide, tetramethylethylenediamine,benzotriazole and a mixture of them. An amount of the curing inhibitoris preferably 0.001 to 1.0 part by mass, further preferably 0.005 to 0.5part by mass, relative to the total 100 parts by mass of components (A)to (D).

Other Additives

The present silicone composition may comprise other additives besidesthe aforesaid components. Examples of the other additives includeanti-aging agents, radical polymerization inhibitors, flame retardants,surfactants, antiozonants, light stabilizers, thickeners, plasticizers,antioxidants, heat stabilizers, electrical conductivity-impartingagents, antistatic agents, radiation insulating agents, nucleatingagents, phosphorus-type peroxide decomposers, lubricants, pigments,metal-inactivating agents, physical property-adjusting agents andorganic solvents. These optional components may be used singly or incombination of two or more of them.

The simplest embodiment of the present silicone composition consists ofcomponents (A), (B), (C) and (0). The composition consisting ofcomponents (A), (B), (C) and (D) and the fluorescent material is alsopreferred. In particular, it is preferred that the composition does notcomprise any inorganic filler such as silica, in order to prepare acured product having a higher transparency. The inorganic filler is asdescribed above.

The present curable composition may be prepared in any known manners.For instance, the composition may be prepared by mixing component (A),component (B), component (C) and component (D) in any manner. Meanwhile,the composition may be prepared by mixing component (A), component (B),component (C), component (D) and the fluorescent material and/or theother components in any manner. For instance, the aforesaid componentsare placed in a commercial stirrer, such as THINKY CONDITIONING MIXER,ex Thinky Corporation, and mixed homogeneously for about 1 to 5 minutesto prepare the present silicone composition.

The present curable composition may be cured in any known manners.Curing conditions are not particularly limited. For instance, thecomposition may be cured at 60 to 180 degrees C. for 1 to 12 hours. Inparticular, the composition is cured stepwise in the range of 60 to 150degrees C. The stepwise curing preferably consists of the following twosteps. The curable composition is first heated at 60 to 100 degrees C.for 0.5 to 2 hours to be defoamed sufficiently. Subsequently, thecomposition is heated at 120 to 180 degrees C. for 1 to 10 hours tocure. Through these steps, the composition is sufficiently cured, nobubble occur and the cured product is colorless and transparent, evenwhen a cured product has a large thickness. In the presentspecification, “colorless and transparent” means that a lighttransmittance at 450 nm of a cured product having a thickness of 1 mm is80% or more, preferably 85% or more, particularly preferably 90% ormore.

The curable composition provides a cured product having a high opticaltransparency. Accordingly, the present silicone composition is useful asan encapsulating material for LED elements, in particular blue LEDelements and violet LED elements. The encapsulation of LED elements withthe present curable composition may be carried out in any known manners.For instance, a dispense method and a compression molding method may beused.

On account of the properties such as excellent crack resistance, heatresistance, light resistance and transparency, the present curablecomposition and cured product are useful also as materials for displays,optical recording mediums, optical apparatus, optical components andoptical fibers, and photo/electron functional organic materials andmaterials for integrated semiconductor circuit-related elements.

EXAMPLES

The present invention will be explained below in further detail withreference to a series of the Examples and the Comparative Examples,though the present invention is in no way limited by these Examples.

In the following descriptions, the weight average molecular weight (Mw)was determined by gel permeation chromatography, i.e., GPC, and reducedto polystyrene. Conditions in the GPC were as follows.

[GPC Conditions]

Solvent: Tetrahydrofuran

Flow rate: 0.6 mL/min.

Columns: all provided by TOSOH Cop.

TSK Guardcolumn SuperH-L

TSKgel SuperH4000(6.0 mmI.D.×15 cm×1)

TSKgel SuperH3000(6.0 mmI.D.×15 cm×1)

TSKgel SuperH2000(6.0 mmI.D.×15 cm×2)

Column Temperature: 40 degrees C.

Injection Volume: 20 micro liters of a 0.5% by weight solution in THF.

Detector: Differential refractive index detector (RI)

An amount of a Vi group (mol/100 g) and an amount of an SiH group(mol/100 g) were calculated from a value of an integral value of ahydrogen atom which was obtained in ¹H-NMR spectra at 400 MHz, usingdimethylsulfoxide as an internal standard. The ¹H-NMR spectra wasobtained with ULTRASHIELD™ 400PLUS, ex BRUKER Corporation. ²⁹Si-NMRspectra was obtained with RESONANCE500, ex JEOL Ltd.

The synthesis example of component (A) used in the Examples will bedescribed below. In the following, Me is abbreviation for a methyl groupand Ph is abbreviation for a phenyl group.

Synthesis Example 1

(a-1)

96.3 Grams of lithium trimethylsilanolate, 1,560 grams ofhexamethylcyclotrisiloxane, and 4,160 grams ofhexaphenylcyclotrisiloxane were added in toluene, stirred at 100 degreesC. for 12 hours and, then, neutralized with 90.0 grams of acetic acid.The product obtained was filtrated. Then, 408 grams ofmethyltrimethoxysilane and 8.10 grams of Sr(OH)₂. 8H₂O were added to theresidue and stirred at 60 degrees C. for 3 hours. Then, 12.2 grams ofacetic acid were added to the reaction mixture to neutralize it, theproduct obtained was filtrated, and methanol and toluene were distilledoff at a reduced pressure to thereby obtain an organopolysiloxane (a-1)which has two alkoxy groups at one terminal and represented by thefollowing formula. Its Mw was 6,000.

wherein c and c′ are 20.(A-1)

600 Grams of the organopolysiloxane obtained in the step (a-1), 140grams of polymethylphenylsiloxane-α,ω-diol, Mw=530, and 0.810 gram ofSr(OH)₂.8H₂O were mixed and stirred at 60 degrees C. for 18 hours. Then,1.22 grams of acetic acid were added to the mixture to neutralize it.17.1 Grams of chlorodimethylvinylsilane were added to the mixture andstirred at 60 degrees C. for 8 hours. The mixture was filtrated. Theresidue was washed with water, and, then, subjected to azeotropicdehydration, and the solvent was distilled off to obtain a branchedsilicone oil represented by the following formula, hereinafter referredto as organopolysiloxane (A-1). Its Mw was 27,000. The amount of the Vigroup was 7.41×10⁻³ mol/100 g. The organopolysiloxane (A-1) was analyzedby ‘Si-NMR to find that in the following formula, a was 4, b was 40, cwas 20 and c’ was 20.

Synthesis Example 2

(a-2)

96.3 Grams of lithium trimethylsilanolate, 222 grams ofhexamethylcyclotrisiloxane, and 595 grams of hexaphenylcyclotrisiloxanewere added in toluene, stirred at 100 degrees C. for 3 hours and, then,neutralized with 90.0 grams of acetic acid. The product obtained wasfiltrated. Then, 408 grams of methyltrimethoxysilane and 8.10 grams ofSr(OH)₂.8H₂O were added to the residue and stirred at 60 degrees C. for3 hours. Then, 12.2 grams of acetic acid were added to the reactionmixture to neutralize it, the product obtained was filtrated, andmethanol and toluene were distilled off at a reduced pressure to therebyobtain an organopolysiloxane (a-2) which has two alkoxy groups at oneterminal and represented by the following formula. Its Mw was 1,000.

wherein c and c′ are 3.(A-2)

100 Grams of the organopolysiloxane obtained in the step (a-2), 27.9grams of polymethylphenylsiloxane-α,ω-diol, Mw=530, and 0.64 gram ofSr(OH)₂.8H₂O were mixed and stirred at 60 degrees C. for 3 hours. Then,0.960 gram of acetic acid was added to the mixture to neutralize it.24.4 Grams of chlorodimethylvinylsilane were added to the mixture andstirred at 60 degrees C. for 8 hours. The mixture was filtrated. Theresidue was washed with water, and, then, subjected to azeotropicdehydration, and the solvent was distilled off to obtain a branchedsilicone oil represented by the following formula, hereinafter referredto as organopolysiloxane (A-2). Its Mw was 3,300. The amount of the Vigroup was 6.06×10⁻² mol/100 g. The organopolysiloxane (A-2) was analyzedby ²⁹Si-NMR to find that in the following formula, a was 3, b was 6, cwas 3 and c′ was 3.

Synthesis Example 3

(a-3)

90.1 Grams of trimethylsilanol, 6,660 grams ofhexamethylcyclotrisiloxane, and 121 grams of sodium salt of phenylsiloxydicatechol were added in acetonitrile, stirred at 60 degrees C. for 12hours. The product obtained was filtrated. Then, 408 grams ofmethyltrimethoxysilane and 8.10 grams of Sr(OH)₂.8H₂O were added to theresidue and stirred at 60 degrees C. for 3 hours. Then, 12.2 grams ofacetic acid were added to the reaction mixture to neutralize it, theproduct obtained was filtrated, and methanol and toluene were distilledoff at a reduced pressure to thereby obtain an organopolysiloxane (a-3)which has two alkoxy groups at one terminal and represented by thefollowing formula. Its Mw was 6,800.

wherein c is 90.(A-3)

680 Grams of the organopolysiloxane obtained in the step (a-3), 72.0grams of polydimethylsiloxane-α,ω-diol, Mw=280, and 3.76 grams ofSr(OH)₂.8H₂O were mixed and stirred at 60 degrees C. for 18 hours. Then,5.64 grams of acetic acid were added to the mixture to neutralize it.13.0 Grams of chlorodimethylvinylsilane were added to the mixture andstirred at 60 degrees C. for 8 hours. The mixture was filtrated. Theresidue was washed with water, and, then, subjected to azeotropicdehydration, and the solvent was distilled off to obtain a branchedsilicone oil represented by the following formula, hereinafter referredto as organopolysiloxane (A-3). Its Mw was 73,000. The amount of the Vigroup was 2.74×10⁻³ mol/100 g. The organopolysiloxane (A-3) was analyzedby ²⁹Si-NMR to find that in the following formula, a was 10, b was 90,and c was 90.

Synthesis Example 4

(a-4)

90.1 Grams of trimethylsilanole, 890 grams ofhexamethylcyclotrisiloxane, and 121 grams of sodium salt of phenylsiloxydicatechol were added in acetonitrile, stirred at 60 degrees C. for 6hours. The product obtained was filtrated. Then, 408 grams ofmethyltrimethoxysilane and 8.10 grams of Sr(OH)₂.8H₂O were added to theresidue and stirred at 60 degrees C. for 3 hours. Then, 12.2 grams ofacetic acid were added to the reaction mixture to neutralize it, theproduct obtained was filtrated, and methanol and toluene were distilledoff at a reduced pressure to thereby obtain an organopolysiloxane (a-4)which has two alkoxy groups at one terminal and represented by thefollowing formula. Its Mw was 1,000.

wherein c is 12.

(A-4)

1,000 Grams of the organopolysiloxane obtained in the step (a-4), 12.0grams of polydimethylsiloxane-α,ω-diol, Mw=280, and 5.06 grams ofSr(OH)₂.8H₂O were mixed and stirred at 60 degrees C. for 18 hours. Then,7.59 grams of acetic acid were added to the mixture to neutralize it.340 Grams of chlorodimethylvinylsilane were added to the mixture andstirred at 60 degrees C. for 8 hours. The mixture was filtrated. Theresidue was washed with water, and, then, subjected to azeotropicdehydration, and the solvent was distilled off to obtain a branchedsilicone oil represented by the following formula, hereinafter referredto as organopolysiloxane (A-4). Its Mw was 81,000. The amount of the Vigroup was 2.74×10⁻³ mol/100 g. The organopolysiloxane (A-4) was analyzedby ²⁹Si-NMR to find that in the following formula, a was 80, b was 12,and c was 12.

Comparative Example 1

(A-1′)

Phenylmethylsilicone oil which has vinyl groups at the both terminalsand represented by the following formula, ex Shin-Etsu Chemical Co.,Ltd. The amount of the Vi group was 3.81×10⁻² mol/100 g.

Comparative Example 2

(A-2′)

Dimethylsilicone oil which has vinyl groups at the both terminal andrepresented by the following formula, ex Shin-Etsu Chemical Co., Ltd.The amount of the Vi group was 1.33×10⁻² mol/100 g.

wherein n is 200 on average.

Comparative Example 3

(A-3′)

63.7 Grams of 1,1-diphenyl-1,3-dimethyl-3,3-dimethoxydisiloxane, 1,200grams of polymethylphenylsiloxane-α,ω-diol, Mw=530, and 48.8 grams ofdimethylvinylmethoxysilane were mixed and heated to 60 degrees C. 3.15Grams of Sr(OH)₂.8H₂O were added to the mixture and, then, thesecompounds were reacted at 60 degrees C. for 3 hours. The catalyst wasremoved from the reaction mixture by filtration and, then, methanol andwater were distilled off at a reduced pressure to obtain a branchedsilicone oil represented by the following formula. Its Mw was 5,700. Anamount of the Vi group was 3.51×10⁻² mol/100 g. The organopolysiloxanewas analyzed by ²⁹Si-NMR to find that in the following formula, n was 37and m was 1.

Components (B), (C) and (D)

Components (B), (C) and (D) used in the following Examples are asfollows.

(B-1) Phenyl type silicone resin represented by the following formula,which has 0.147 mol/100 g of a Vi group and 1,600 of weight-averagemolecular weight, ex Shin-Etsu Chemical Co., Ltd.:

wherein n is 3 and m is 10.

(B-2) Methyl type silicone resin represented by the following formula,which has 9.12×10⁻² mol/100 g of a Vi group and 5,800 of weight-averagemolecular weight, ex Shin-Etsu Chemical Co., Ltd.:

wherein n is 5, m is 30 and j is 48.

(C-1) Silicone oil which is represented by the following formula, hashydrosilyl groups at both terminals and has 0.600 mol/100 g of an SiHgroup, ex Shin-Etsu Chemical Co., Ltd.:

(C-2) Silicone oil which is represented by the following formula, hashydrosilyl groups as a side chain and has 1.63 mols/100 g of an SiHgroup, ex Shin-Etsu Chemical Co., Ltd.:

wherein n is 38 on average.

(D) Solution of divinylsiloxane complex of platinum chloride inisododecane containing a platinum metal of 0.5 mass %.

Example 1

100 Parts by mass of component (A-1), 300 parts by mass of component(B-1), 81 parts by mass of component (C-1) were mixed and then,divinylsiloxane complex of platinum chloride was added in an amount,reduced as a platinum metal, of 5 ppm relative to the total mass of themixture, to obtain the curable composition.

Examples 2 to 4 and Comparative Examples 1 to 3

The manner of Example 1 was repeated, except that the amounts of thecomponents were changed as seen in Table 1 to obtain curablecompositions.

The curable compositions prepared in Examples 1 to 4 and ComparativeExamples 1 to 3 were evaluated according to the following manners.

[1. Viscosity of the Curable Compositions]

The viscosity of the curable composition was determined with a B-typeviscometer at 23 degrees C. according to the Japanese IndustrialStandards (JIS) Z 8803:2011. The results are as shown in Table 1.

[2. Hardness of the Cured Products]

The curable composition was poured into an aluminum petri dish having adiameter of 50 mm and a depth of 10 mm and, then, heated at 60 degreesC. for one hour, 100 degrees C. for one hour and, subsequently 150degrees C. for 4 hours to obtain a cured product. A hardness of thecured product was determined with durometer type A or D according to theJapanese Industrial Standards (JIS) K 6253-3:2012. The results are asshown in Table 1.

[3. Light Transmittance of the Cured Products]

A concave Teflon(Trademark) spacer having a depth of 1 mm was sandwichedby two glass slides having dimensions of 50 mm×20 mm×1 mm and tightlyheld. The curable composition was poured into the dent of the concaveTeflon spacer and heated at 60 degrees C. for one hour, 100 degrees C.for one hour and, subsequently 150 degrees C. for 4 hours to cure, toobtain a sample. A transmittance at 450 nm of the sample was determinedwith a spectrophotometer, U-4100, ex Hitachi High-TechnologiesCorporation. The results are as shown in Table 1.

[4. Tensile Strength and Elongation at Break of the Cured Products]

The curable composition was poured into a Teflon-coated mold having acavity of 150 mm×200 mm×2 mm, and cured stepwise at 60 degrees C. forone hour, 100 degrees C. for one hour and, subsequently 150 degrees C.for 4 hours to obtain a sample. A tensile strength and elongation atbreak of the cured product were determined according to JIS K 6251:2010with EZ TEST, EZ-L, ex Shimadzu Corporation, in the followingconditions: a tensile speed was 500 mm/min, a distance between clampswas 80 mm, and a distance of gauge points was 40 mm. The results are asshown in Table 1.

[5. Glass-Transition Temperature of the Cured Products]

The storage elastic modulus, MPa, of the cured product prepared as in 4.above procedures was determined at a temperature between −140 degrees C.and 150 degrees C. with DMA Q800, ex TA Instruments. A temperature at apeak in a curved of tangent δ, calculated from obtained storage elasticmodulus vs temperature is a glass transition temperature (Tg).

The storage elastic modulus was determined in the following conditions:the sample had a length of 20 mm, a width of 5 mm and a thickness of 1mm, a rate of temperature rise was 5° C./minute; and a multi-frequencymode, a tension mode, and an amplitude of 15 μm. The results are asshown in Table 1. FIG. 1 shows the storage elastic modulus and theTangent δ of the Examples (solid line) and these of the ComparativeExamples (dotted line).[6. Thermal Cycle Test]

The curable composition was dispensed on a Tiger3528 package, exShin-Etsu Chemical Co., Ltd., and heated at 60 degrees C. for one hour,subsequently at 100 degrees C. for one hour and, then, at 150 degrees C.for four hours to cure, to obtain a sample package encapsulated with thecured product. 20 test samples were subjected to a thermal cycle test(TCT) with 1000 thermal cycles of −50 to 140 degrees C. When the curedproduct had cracks, it was evaluated as NG. When the test package had nocrack, it was evaluated as OK. Number of NG are as shown in Table 1.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Com. Ex. 1 Com. Ex. 2 Com. Ex. 3Component (A) (A-1) 100 — — — — — — (A-2) — 100 — — — — — (A-3) — — 100— — — — (A-4) — — — 100 — — — (A-1′) — — — — 100 — — (A-2′) — — — — —100 — (A-3′) — — — — — — 100 Component (B) (B-1) 300 300 — — 300 — 300(B-2) — — 100 100 — 100 — Component (C) (C-1) 75 293 — — 80 — 119 (C-2)— — 8.6 4 — 13 — H/Vi 1 3.5 1.5 0.7 1 2 1.5 Evaluation Viscosity 23degrees C. Pa · s 5.6 1.2 10 24 7.3 8.9 0.2 Hardness Shore A — — — 60 35— 70 40 Shore D — 40 30 — — 45 — — Transmittance Thickness of 1 mm, % T99.4 99.3 99.3 99.3 99.4 99.4 99.5 450 nm Tensile strength 25 degrees C.MPa 4.2 2.1 7.1 3.5 4.8 6.8 2.6 Elongation at break 25 degrees C. % 7030 120 100 60 100 70 Tg By DMA degrees C. 18 12 −103 −112 35 −120 3Thermal cycle test 1000 thermal cycles Number of 0/20 0/20 0/20 0/2020/20 12/20 18/20 of −50 to/from 140 NG degrees C.In Table 1, H/Vi is a ratio of the total number of the SiH groups in thecomposition to the total number of the vinyl groups in the composition.NG is the number of the cracked samples.

As seen in Table 1, the present curable silicone resin compositionscomprising the present branched organopolysiloxane provided the curedproducts having a lower glass-transition temperature and an excellentcrack resistance, compared to the compositions comprising the linearorganopolysiloxane in place of the present branched organopolysiloxane.Additionally, the present resin compositions have a low viscosity and,accordingly its workability is good.

INDUSTRIAL APPLICABILITY

The present invention provides the addition-curable siliconecompositions which has good low-temperature properties andtemperature-change resistance, and a semiconductor device having anexcellent reliability, which semiconductor element is encapsulated withthe cured product of the present composition.

The invention claimed is:
 1. A semiconductor device comprising asemiconductor element encapsulated with a cured product obtained bycuring an addition-curable silicone resin composition comprising (A) abranched organopolysiloxane represented by the following formula (1):

wherein R¹ is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atomsor a substituted or unsubstituted, aromatic hydrocarbon group having 6to 12 carbon atoms, R² is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,a substituted or unsubstituted, aromatic hydrocarbon group having 6 to12 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, R¹ andR² may be the same as or different from each other, at least two of R²are each an alkenyl group, a is an integer of from 2 to 100, b is aninteger of from 5 to 100, c is an integer of from 5 to 100,0.03≤a/(a+b)<1.0, and a ratio of the number of (R¹ ₂R²SiO_(1/2)) unit tothe number of (R²SiO_(3/2)) unit is 2 or less, wherein the parenthesizedsiloxane units may bond randomly or form a block unit; (B) anorganopolysiloxane represented by the following formula (2):(R² ₃SiO_(1/2))_(r)(R²₂SiO_(2/2))_(s)(R²SiO_(3/2))_(t)(SiO_(4/2))_(u)  (2) wherein R² is asdefined above, at least two of R² are each an alkenyl group, r is aninteger of from 0 to 100, s is an integer of from 0 to 300, t is aninteger of from 0 to 200, and u is an integer of from 0 to 200, providedthat a total oft and u is 1 to 400 and a total of r, s, t and u is 2 to800 in an amount of 5 to 900 parts by mass, relative to 100 parts bymass of component (A), (C) an organopolysiloxane having at least twohydrosilyl groups, in an amount such that a ratio of the number of thehydrosilyl groups in component (C) to the number of the alkenyl groupsin components (A) and (B) is 0.4 to 4.0, and (D) a hydrosilylationcatalyst in an amount sufficient to accelerate hydrosilylation.
 2. Thesemiconductor device according to claim 1, wherein the semiconductorelement is a light emitter.
 3. A method for preparing anaddition-curable silicone resin composition wherein the method comprisessteps of subjecting an organopolysiloxane represented by the followingformula (4):

wherein R¹ is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atomsor a substituted or unsubstituted, aromatic hydrocarbon group having 6to 12 carbon atoms, R² is, independently of each other, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,a substituted or unsubstituted, aromatic hydrocarbon group having 6 to12 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, R¹ andR² may be the same as or different from each other, at least two of R²are each an alkenyl group, c is an integer of from 5 to 100, and R³ is ahydrogen atom or a saturated hydrocarbon group having 1 to 6 carbonatoms, to a co-condensation reaction with an organopolysiloxanerepresented by the following formula (5):

wherein R² and R³ are as defined above, b′ is at least 1 and at mostsame as b, and b is an integer of from 5 to 100, and subsequently anend-capping reaction with a hydrolyzable group-containing silanecompound represented by the following formula (6):

wherein R¹ and R² are as defined above, X is a halogen atom or a grouprepresented by R³O—, wherein R³ is as defined above, to thereby obtain areaction product (A), and mixing the reaction product (A) with thefollowing components (B), (C) and (D) to thereby prepare theaddition-curable silicone resin composition, (B) an organopolysiloxanerepresented by the following formula (2):(R² ₃SiO_(1/2))_(r)(R²₂SiO_(2/2))_(s)(R²SiO_(3/2))_(t)(SiO_(4/2))_(u)  (2) wherein R² is asdefined above, at least two of R² are each an alkenyl group, r is aninteger of from 0 to 100, s is an integer of from 0 to 300, t is aninteger of from 0 to 200, and u is an integer of from 0 to 200, providedthat a total oft and u is 1 to 400 and a total of r, s, t and u is 2 to800, in an amount of 5 to 900 parts by mass, relative to 100 parts bymass of component (A), (C) an organopolysiloxane having at least twohydrosilyl groups, in an amount such that a ratio of the number of thehydrosilyl groups in component (C) to the number of the alkenyl groupsin components (A) and (B) is 0.4 to 4.0, and (D) a hydrosilylationcatalyst in an amount sufficient to accelerate hydrosilylation.
 4. Themethod according to claim 3, wherein the reaction product (A) has amonovalent aromatic hydrocarbon group bonded to a silicon atom, in anamount of from 3% or more to 90% or less in number, based on a totalnumber of the groups each bonded to a silicon atom.
 5. The methodaccording to claim 3 or 4, wherein component (C) is represented by thefollowing formula (3):(R³ ₃SiO_(1/2))_(r′)(R³₂SiO_(2/2))_(s′)(R³SiO_(3/2))_(t′)(SiO_(4/2))_(u′)  (3) wherein R³ is,independently of each other, a hydrogen atom, a substituted orunsubstituted, saturated hydrocarbon group having 1 to 12 carbon atoms,or a substituted or unsubstituted, aromatic hydrocarbon group having 6to 12 carbon atoms, at least two of R³ are each a hydrogen atom, r′ isan integer of from 0 to 100, s′ is an integer of from 0 to 300, t′ is aninteger of from 0 to 200, and u′ is an integer of from 0 to 200, a totalof r′, s′, t′ and u′ is 2 to 800.